1). Field of the Invention
This invention relates to a valve, a method of operating a valve, and a method of operating a sterilization unit.
2). Discussion of Related Art
Sterilization units are commonly used for sterilizing objects such as surgical and other medical equipment. A sterilization unit of this kind which is commonly used includes a sterilization chamber into which objects such as surgical and other medical equipment are located. The pressure within the sterilization chamber is then reduced by pumping air out of the sterilization chamber through a valve which is located in line between the sterilization chamber and a pump. The valve controls the flow of the air to the pump. Once the pressure within the sterilization chamber is suitably reduced, a valve member within the valve is alternatingly opened and closed, or xe2x80x9cthrottledxe2x80x9d, to maintain the pressure within the sterilization chamber within relatively tight parameters.
The valve has a flow passage therethrough with a cross-sectional area which is optimally chosen both for quick discharge of air from the sterilization chamber and for accurately controlling the pressure within the sterilization chamber by throttling. The valve also has inlet and outlet openings which are chosen so as to match an outlet from the sterilization chamber and an inlet into the pump, respectively.
Sterilization units differ from one another because they have smaller or larger sterilization chambers and pumps, depending on requirement. Sterilization chambers of different sterilization units typically have 72 liter, 170 liter, or 270 liter internal volumes. The flow rates required to quickly reduce pressures or more accurately control pressures within the respective chambers therefore differ from one another. A different size valve and pump are therefore required on each of the different size sterilization chambers. Ideally, one design valve should, at least in part, be usable on sterilization chambers having different internal volumes while still allowing both for quick discharge of air or other fluids from, and for accurate control of pressures, of different size sterilization chambers by throttling. Ideally, the valve should be simple in design and should preferably not, for example, be a butterfly valve or a gate valve which is expensive to manufacture.
Some processes disclose using two valves for controlling pressure within a sterilization chamber, such as in U.S. Pat. No. 5,851,485 assigned to Johnson and Johnson Medical, Inc. of New Brunswick, N.J. which is for a system other than the system which is described herein.
According to one aspect of the invention a valve is provided which includes a valve body, a first valve member, and a second valve member. The valve body has a first flow passage formed therethrough and a second flow passage formed therein. The first flow passage has a first cross-sectional area and has first and second portions. The second flow passage has a second cross-sectional area which is smaller than the first cross-sectional area and has first and second sections. The first section has an end terminating in the first portion, and the second section has an end terminating in the second portion. The first valve member is mounted to the body for movement between substantially open and substantially closed positions. In the open position the first and second portions are in communication with one another to allow for flow of fluid into the first portion, from the first portion into the second portion, and from the second portion out of the valve body. In the closed position, the first valve member substantially closes off communication between the first and second portions. The second valve member is mounted to the body for movement, independently from the first valve member, between substantially unshut and substantially shut positions. In the unshut position the first and second sections are in communication with one another to allow for flow of fluid from the first portion into the first section, from the first section into the second section, and from the second section into the second portion. In the shut position, the second valve member substantially closes off communication between the first and second sections.
The body is preferably made of material which is resistant to attack by hydrogen peroxide.
The first flow passage may include an annular seat and the first valve member may be a first plug member. The first plug member may have a sealing surface which, when the first plug member is in the open position, is displaced from the annular seat and, when the first plug member is in its closed position, seals circumferentially with the annular seat.
The valve body may include a main portion and a cap secured to the main portion so that the main portion and the cap jointly define the second portion of the first flow passage. The cap may have a shaft opening formed therein. The valve may further include a shaft which extends through the shaft opening into the valve body, and the first plug member may be secured to the shaft inside the valve body.
The first portion may form an inlet opening into the valve body having a cross-sectional area of at least 490 mm2, and the second portion may form an outlet opening out of the valve body having a cross-sectional area of at least 490 mm2. The inlet opening may have a cross-sectional area of at least 1250 mm2 and the outlet opening may have a cross-sectional area of at least 1250 mm2. More specifically, the inlet opening may have a cross-sectional area of at least 1960 mm2 and the outlet opening may have a cross-sectional area of at least 1960 mm2.
The first cross-sectional area may be at least 490 mm2 and the second cross-sectional area may be less than 28 mm2, in which case the first cross-sectional area may be at least 1250 mm2, or may be at least 1960 mm2.
The first portion may form an inlet opening into the valve body and the second portion may form an outlet opening out of the valve body and the valve may further include an adapter having a flow aperture formed therethrough. The flow aperture may have an aperture inlet and an aperture outlet which is larger than the aperture inlet. The adapter may be secured to the valve body so that the aperture outlet is located adjacent the inlet opening into the valve body.
The aperture inlet may have a cross-sectional area of less than 630 mm2.
The aperture outlet may have a cross-sectional area of at least 1250 mm2, or even a cross-sectional area of at least 1960 mm2.
The aperture inlet may have a cross-sectional area of less than 1260 mm2, in which case the aperture outlet may have a cross-sectional area of at least 1960 mm2.
The second flow passage may be formed by a first hole in the valve body, and a second hole which extends out of the first hole intermediate ends thereof, and the body may further have a plug aperture formed therein and extending into the first hole on a side thereof opposing and over the second hole. The second valve member may be a second plug member which, when in the shut position is located over an end of the second hole, and moves away from the end of the second hole into the plug aperture when moving from the shut position into the unshut position.
The first hole may extend out of an outer surface of the valve body. The valve may further include a plug which closes off an end of the first hole extending out of the valve body.
The invention also provides a method of operating a valve. A first valve member is moved between substantially closed and substantially open positions so as to control flow of a fluid through a first flow passage to a valve body of the valve. A second valve member is moved between substantially unshut and substantially shut positions so as to control flow of the fluid through a second flow passage in the valve body, the second flow passage interconnecting first and second portions of the first flow passage on opposing sides of the first valve member when in the closed position, and having a cross-sectional area which is smaller than a cross-sectional area of the first flow passage.
The valve may be located in line between a chamber and a pump. The first valve member may be moved into the open position so as to reduce the pressure within the chamber from a high pressure to a low pressure. Thereafter, the second valve member may be alternatingly moved between the unshut and shut positions to maintain the pressure within the chamber below the high pressure.
The chamber may have an internal volume of at least 50, at least 100 liters, or at least 200 liters. The first valve member may be in the closed position when the second valve member is alternatingly moved between the unshut and shut positions.
Alternatively, the chamber may have an internal volume of at least 800 liters.
The invention also provides a sterilization unit comprising of a sterilization chamber, an inlet valve, a pump, and an outlet valve. The sterilization chamber has an inlet and an outlet. The inlet valve opens and closes the inlet into the sterilization chamber. The outlet valve is located in line between the outlet of the sterilization chamber and the pump. The outlet valve includes a valve body, a first valve member, and a second valve member. The valve body has a first flow passage formed therethrough and second flow passage formed therein. The first flow has a first cross-sectional area and having a first and second portions. The second flow passage has a second cross-sectional area which is smaller than the first cross-sectional area and has first and second sections. The first section has an end terminating in the first portion, and the second section has an end terminating in the second portion. The first valve member is mounted to the body for movement between open and closed positions. In the open position, the first and second portions are in communication with one another to allow for flow of fluid from the sterilization chamber into the first portion, from the first portion into the second portion, and from the second portion to the pump. In the closed position, the first valve member substantially closes off communication between the first and second portions. The second valve member is mounted to the body for movement, independently of the first valve member between unshut and shut positions. In the unshut position the first and second sections are in communication with one another to allow for flow of fluid from the first portion into the first section, from the first section into the second section, and from the second section into the second portion. In the shut position, the second valve member substantially closes off communication between the first and second sections.
The first flow passage preferably includes an annular seat and the first valve member is preferably a first plug member having a sealing surface. which, when the first plug member is located in the open position, is spaced from the annular seat and, when the first plug member is in the closed position, seals circumferentially with the annular seat.
The valve body may include a main portion and a cap. The cap may have a shaft opening from therein and may be secured to the main portion so that the main portion and the cap jointly define the second portion of the first flow passage. The valve may further include a shaft which extends through the shaft opening into the valve body, wherein the first plug member is secured to the shaft inside the valve body.
The invention also provides a method of operating a sterilization unit comprising a sterilization chamber and at least one pump. A first valve member is moved from substantially a closed position to substantially an open position so as to allow flow of fluid through a first flow passage, formed through a valve body, to the at least one pump. The valve member is then moved from the substantially open position to the substantially closed position. A second valve member is then alternatingly moved between substantially unshut and substantially shut positions to control flow of fluid through a second flow passage through a valve body to the at least one pump. The second flow passage has a cross-sectional area which is smaller than a cross-sectional area of the first flow passage.
The valve body through which the first flow passage is formed may be the same valve body through which the second flow passage is formed.
When the valve member is alternating moved between the unshut and shut positions, the pressure within the chamber is preferably so maintained between 300 milliTorr and 1000 milliTorr.